Adrenomedullin is a 52-amino acid peptide first described in 1993 (Kitamura, et al., Biochem. Biophys. Res. Commun. 192:553-560 (1993)). It was originally identified in a human pheochromocytoma and has since been found to be in normal adrenal medulla and in many other tissues including the atria, ventricles, endothelial cells, lungs, brain and kidneys (Kitamura, K., et al., Biochem. Biophys. Res. Commun. 192:553-560 (1993); Kitamura, K., et al., Biochem. Biophys. Res. Commun. 192:720-725 (1993); Ichiki, Y., et al., FEBS Lett. 338:6-10 (1994); Katoh, F., et al., FEBS Lett. 348:61-64 (1994); Sakata, J., et al., Biochem. Biophys. Res. Commun. 195:921-927 (1993); Sugo, S., et al., Biochem. Biophys. Res. Commun. 201:1160-1166 (1994); Sugo, S., et al., Biochem. Biophys. Res. Commun. 203:719-726 (1994); Jougasaki, M., et al., Am. J. Physiol. 268:F657-F663 (1995); Satoh, F., et al., J. Clin. Endocrinol. Metab. 80:1750-1752 (1995); and Jougasaki, M., et al., Circulation 92:286-289 (1995)). It circulates in picomolar concentrations in both rats and man (Kitamura, K., et al., FEBS Lett. 341:288-290 (1994); Sakata, J., et al., FEBS Lett. 352:105-108 (1994); Sato, K., et al., Life Sci. 57:189-194 (1995)). It is a potent vasodilator, acting directly on the renal, cerebral, mesenteric, pulmonary, and systemic circulations, and its administration results in hypotension (Seguchi, H., et al., Biochem. Biophys. Res. Commun. 215:619-625 (1995); Nuki, C., et al., Biochem. Biophys. Res. Commun. 196:245-251 (1993); Berthiaume, N., et al., Can. J. Physiol. Pharmacol. 73:1080-1083 (1995); Nakamura, K., et al., Jpn. J. Pharmacol. 67:259-262 (1995); Feng, C. J., et al., Life Sci. 55:PL433-PL438 (1994); and DeWitt, B. J., et al., Eur. J. Pharmacol. 257:303-306 (1994). Its hemodynamic effects are probably mediated via receptors on vascular smooth muscle cells and possibly endothelial cells (Ishizaka, Y., et al., Biochem. Biophys. Res. Commun. 200:642-646 (1994); Eguchi, S., et al., FEBS Lett. 340:226-230 (1994); and Shimekake, Y., et al., J. Biol. Chem. 270:4412-4417 (1995)). Binding to renal tubular membranes has been observed, and sodium, potassium, and water excretion are increased by adrenomedullin (Hirata, Y., et al., Hypertension 25:790-795 (1995); and Ebara, T., et al., Eur. J. Pharmacol. 263:69-73)). Adrenomedullin is a bronchodilator, and it modulates release of pituitary and vasoactive hormones (Tian, Q., et al., Can. J. Physiol. Pharmacol. 73:1065-1069 (1995); Kohno, M., et al., Hypertension 25:1185-1190 (1995); and Yamaguchi, T., et al., Life Sci. 56:379-387 (1994)).